Glass Lewis, in a report, said that the proposed $8 billion deal should be rejected, given the short and opaque process and the "questionable strategic merits" of the merger. It sided with U.S. hedge fund Elliott Associates LP, which is seeking to block the merger, in criticizing the offer's financial terms.

In May, Cheil Industries and Samsung C&T announced plans to merge in an all-stock deal, but days later, Elliott disclosed it had a 7.1% stake in Samsung C&T and filed a court motion to block the deal. Elliot argued the deal undervalued the construction and trading arm of South Korea's biggest conglomerate.

The deal is seen as a key move by Samsung's controlling Lee family to tighten its grip on crown jewel Samsung Electronics Co. ahead of a planned succession. Samsung C&T owns a 4.1% stake in Samsung Electronics.